There seems to be 2 layers of potential difficulty and it's not clear about the realistic complications of either as yet.
First is simply entering the country with the volunteer visa in the passport (so, airport IO refusing entry after arrival).
Second is getting the elite visa attached with the volunteer visa in the passport (although as has been mentioned previously, if they've already approved the application then this seems quite unlikely).
One way around this, if applicable to you, would be to try to get the Elite visa attached in your home country. I'm thinking, that way, if they refuse to attach it when you're still in your home country it should be much faster and easier to get a new passport and then try again.
There is perhaps another layer of issue here in that once you've been refused, does it then become an issue to get it attached even once you have a new passport? That seems to open up a whole new can of worms.